Organophosphorous compounds having polysulfide bridge

ABSTRACT

The invention relates to organophosphorus compounds comprising a polysulfide bridge, to their process of preparation and to their use as coupling agent between an inorganic or metal filler and an elastomer.  
     The compounds correspond to the formula (I) (RO) 2-t R 1   t P(O)—O x —(CH 2 )— y —S z —(CH 2 ) y —O x —P(O)(OR) 2-t R 1   t  in which R represents a hydrogen, an alkyl, an aryl, a trialkysilyl, a trialkylamino or an alkali metal; R 1  represents an alkyl or an aryl; x is 0 or 1; y is an integer from 1 to 22, preferably from 2 to 4; z&gt;3; t is 0 or 1.

The present invention relates to organophosphorus compounds comprising apolysulfide bridge, to their process of preparation and to their use ascoupling agent between an inorganic filler or a metal filler and anelastomer.

It is known to use coupling agents in processes targeted at reinforcingpolymer matrices by inorganic particles. Mention may in particular bemade of the silanes corresponding to the formula(RO)₃Si(CH₂)_(n)S_(m)(CH₂)_(n)Si(OR₃) in which R=Et or Me, n=2 or 3, m=2or 4 (DE 2141159), or in which R=Et, n=2 or 3, m=2 or 4 (DE 3311340), orin which R=Et, n=3, m=4 (DE 10015308). The improvement in the mechanicalproperties originates from the increase in the adhesion between thepolymer matrix and the inorganic filler. These coupling agents of thesilane type are particularly effective when the inorganic particles aresilica or clays. However, the improvement in the mechanical propertiesof the matrix is smaller when the inorganic filler comprises, forexample, titanium oxide or calcium carbonate and the adhesion with metalsurfaces is poor.

In addition, it is known that the use of compounds of the phosphate,phosphonate or phosphinate type, as a replacement for compounds of theorganosilane type, makes possible good adhesion of the phosphatecompound to inorganic materials, such as metal oxides or metal surfaces.For example, G. Guerrero et al. [(2001), J. Mater. Chem, 11(12),3161-3165] describes the grafting of phenylphosphonic acid or its ethylor trimethylsilyl esters to alumina. G. Guerrero et al. [(2001), Chem.Mater., 13, 4367-4373] describes the grafting of phenylphosphonic acidor phenylphosphinic acid or their ethyl or trimethylsilyl esters toTiO₂. The formation of phosphonic acid monolayers on metal surfaces madeof steel, aluminum, copper or brass is described by J. G. Alsten[Langmuir, (1999) 15, 7605-7614]. T. Nakatsuka [Polym. Prep., Am. Chem.Soc., Div. Polym. Chem., (1983) 24(1), 202-203] describes the graftingof various phosphates, in particular (HO)₂P(O)—OC₈H₁₇, to CaCO₃. The useof an additive of the mercaptoalkyl-phosphonate type in elastomercompositions which comprise silica is described in U.S. Pat. No.4,386,185; the additive is a phosphonate (RO)₂P(O)—(CR′₂)_(n)SH, R beingan alkyl, a cycloalkyl or an arylalkyl, R′ being H or an alkyl and nbeing 1 to 8. The preparation of phosphorus compounds used as catalystsis disclosed in EP-1 157 994; the compounds correspond to the formula(MO)_(m)P(O)(OX)_(n)(R)_(p)[—(O)_(x)—(Z-A)]_(q) in which M is amonovalent cation, m+n+p+x=3, R=hydrocarbon, X=hydrocarbon ortrialkylsilane and A can comprise sulfur originating, for example, froma thiol or an SO₃ group.

It is known that the use of compounds of the monoalkoxytitanate type ascoupling agent makes it possible to increase the amount of inorganicfiller added to a thermoplastic material, without harming its fluidity(S. Monte et al., (1976) Proc., Annu. Conf., Reinf. Plast./Compos.Inst., Soc. Plast. Ind., 31, 6-E).

Furthermore, compounds of the tetrasodium2,2′-(dithiobis)ethanephosphonate type, of use as a medicament (WO98/14426), and dithioethers of the(HO)₂P(O)—(CH₂)_(m)S₂—(CH₂)_(m)—P(O)(OH)₂ type, of use in reducing thetoxic effect of carboplatin (WO 98/11898), are known. In addition, theuse of disulfides comprising terminal groups of the ethylphosphonatetype, as additive in the lubrication of fuels (GB 1 189 304), is known.

The aim of the present invention is to provide compounds of use ascoupling agents between a polymer matrix and an inorganic or metalfiller which exhibit improved properties, in particular with inorganicfillers other than silicas.

A subject matter of the present invention is compounds which correspondto the formula:(RO)_(2-t)R¹_(t)P(O)—O_(x)—(CH_(z))_(y)—S_(z)—(CH₂)_(y)—O_(x)—P(O)(OR)_(2-t)R¹₂  (I)in which:

-   -   R represents a hydrogen, an alkyl, an aryl, a trialkylsilyl, a        trialkylamino or an alkali metal;    -   R¹ represents an alkyl or an aryl;    -   x is 0 or 1;    -   y is an integer from 1 to 22, preferably from 2 to 4;    -   z≧3;    -   t is 0 or 1.

In the compounds of the invention, when R is an alkyl group, it ispreferably chosen from alkyl radicals having from 1 to 6 carbon atoms.When R is an aryl group, it is preferably chosen from phenyl, benzyl andtolyl. The trialkylsilyl group is preferably an R′₃Si-group in which theR′ substituents represent identical or different alkyl groups havingfrom 1 to 3 carbon atoms. The trialkylamino group is preferably anR″₃N-group in which the R″ substituents represent identical or differentalkyl groups having from 1 to 5 carbon atoms. When R is an alkali metal,preference is given in particular to Na and K.

The R¹ substituent is preferably an alkyl radical having from 1 to 18carbon atoms or an aryl radical chosen from phenyl, benzyl and tolyl.

It is possible to single out, among the compounds of the invention, thecompounds for which x=0, that is to say the phosphonates(RO)₂P(O)—(CH₂)_(y)—S_(z)—(CH₂)_(y)—P(O) (OR)₂ (II) and the phosphinates(RO)R¹P(O)—(CH₂)_(y)—S_(z)—(CH₂)_(y)—P(O) (OR)R¹ (IV).

In addition, mention may be made of the compounds in which x=1, that isto say the phosphates (RO)₂P(O)—O—(CH₂)_(y)—S_(z)—(CH₂)_(y)—O—P(O) (OR)₂(III) and (RO)R¹P(O)—O—(CH₂)_(y)—S_(z)—(CH₂)_(y)—O—P(O) (OR)R¹ (V).

Preference is very particularly given, among these compounds, to thosewhich have a mean number of sulfur atoms z of between 3 and 5 and moreparticularly the compounds in which z is on average equal to 4.

The compounds according to the invention can be prepared by processesemploying conventional reactions of sulfur and phosphorus chemistry. Afew specific cases are indicated below.

The phosphonate compounds corresponding to the formula (II) in which z=4and R is an alkyl Ra can be prepared, for example, by the followingprocess:

-   -   during a first stage, the trialkyl phosphite P(ORa)₃ (VI) is        reacted with the dibromoalkylene Br-(CH₂)_(y)—Br (VII) at a        temperature of the order of 140° C. in order to obtain        Br—(CH₂)_(y)—P(O) (ORa)₂ (VIII),    -   during a second stage, the phosphonate Br—(CH₂)_(y)—P(O)        (ORa)₂ (VIII) is reacted with Na₂S₄ under reflux of the        methanol. A product is obtained having a mean composition        corresponding to the formula        (RaO)₂P(O)—(CH₂)_(y)—S₄—(CH₂)_(y)—P(O) (ORa)₂  (IIa)        in which Ra is an alkyl.

A phosphinate (IVa) corresponding to the formula (IV) in which R is Raand z=4 can be obtained by a similar process, the reactant P(ORa)₃ (VI)being replaced during the first stage by a reactant P(ORa)₂R¹ (IX).

A phosphonate which corresponds to the formula (II) in which z=4 and Ris a trialkylsilyl R₁₃Si can be obtained by reacting the compound (IIa)with a trialkylsilyl bromide R₁₃SiBr according to the following reactionscheme:(RaO)₂P(O)—(CH₂)_(y)—S₄—(CH₂)_(y)—P(O)(ORa)₂+4R′₃Si→(R′₃SiO)₂P(O)—(CH₂)_(y)—S₄—(CH₂)_(y)—P(O) (OSiR′)₂  (IIb)

A compound (HO)₂P(O)—(CH₂)_(y)—S₄—(CH₂)_(y)—P(O)(OH)₂  (IIc) whichcorresponds to the formula (II) in which z=4 and R is H can be obtainedeither by hydrolysis of the corresponding compound (IIa) or byhydrolysis or by alcoholysis of the corresponding compound (IIb). Thehydrolysis of the compound (IIb) is a mild method which is particularlypreferred.

A phosphate (IIIa) corresponding to the mean formula (III) in which R isH can be obtained by a process in which:

-   -   during a first stage, P(O)Cl₃ is reacted with a compound        HO(CH₂)_(y)Cl in stoichiometric proportions in order to obtain        the compound Cl(CH₂)_(y)OP(O)Cl₂;    -   during a second stage, the compound Cl(CH₂)_(y)OP(O)Cl₂ is        hydrolyzed in order to obtain the compound Cl(CH₂)_(y)OPO₃H₂;    -   during a third stage, Cl(CH₂)_(y)OPO₃H₂ is reacted with Na₂S₄        under reflux of the methanol and then an ion exchange is carried        out in order to obtain the compound        (HO)₂P(O)—O—(CH₂)_(y)—S_(z)—(CH₂)_(y)—O—P(O)(OH)₂.

The reaction scheme corresponding to this process is as follows:P(O)Cl₃+HO(CH₂)_(y)Cl→Cl(CH₂)_(y)OP(O)Cl₂+HClCl(CH₂)_(y)OP(O)Cl₂+2H₂O→Cl(CH₂)_(y)OPO₃H₂+2 HCl 1) MeOH, reflux2 Cl(CH₂)_(y)OPO₃H₂+Na₂S₄→H₂O₃PO(CH₂)_(y)—S₄—(CH₂)_(y)OPO₃H₂+2 NaCl 2)ion exchange

The organophosphorus compounds of the present invention can be used ascoupling agents between inorganic fillers and elastomers in thetechnical fields in which fillers are used to improve the properties ofelastomers. Although the compounds in which R is a trialkylsilyl aresensitive to hydrolysis, they can nevertheless be used as couplingagents. Mention may in particular be made, among inorganic fillers, ofoxides, hydroxides and carbonates, such as, for example, silica,alumina, titanium oxide, silicoaluminates and clays. Mention may also bemade of metallic materials, such as steels, copper and aluminum.

The present invention is described in more detail by the examples whichare given below by way of illustration but to which it is not, however,limited.

EXAMPLE 1 Preparation of (EtO)₂P(O)—(CH₂)₃—S₄—(CH₂)₃—P(O)(OEt)₂

During a first stage, diethyl 3-bromopropylphosphonate(EtO)₂P(O)—(CH₂)₃—Br was prepared in the following way. One equivalentof triethyl phosphite P(OEt)₃ and 1.5 equivalents of 1,3-dibromopropanewere introduced into a reactor under a nitrogen atmosphere. The reactorwas brought to 140° C. and was maintained at this temperature withstirring for 15 hours. After distillation, the compound(EtO)₂P(O)—(CH₂)₃—Br was obtained with a yield of 60% with respect tothe triethyl phosphite introduced.

Subsequently, 1.71 g of Na₂S₄ and 20 ml of anhydrous methanol wereintroduced into a reactor under a nitrogen atmosphere. The reactor washeated to reflux of the methanol and 5 g (2 equivalents) of(EtO)₂P(O)—(CH₂)₃—Br, dissolved in 20 ml of anhydrous methanol, wereadded dropwise. After refluxing for half an hour, the reactor was cooledto ambient temperature. After separation of the NaBr precipitate,evaporation under vacuum and filtration, 30 ml of anhydrous toluene wereadded. After filtration and evaporation under vacuum, 3.7 g of a yellowoil were obtained. The formation of (EtO)₂P(O)—(CH₂)₃—S₄—(CH₂)₃—P(O)(OEt)₂ with a yield of 76% is confirmed by proton NMR and by elementalanalysis.

EXAMPLE 2 Preparation of (Me₃SiO)₂P(O)—(CH₂)₃—S₄—(CH₂)₃—P(O)(OSiMe₃)₂

5 g of (EtO)₂P(O)—(CH₂)₃—S₄—(CH₂)₃—P(O) (OEt)₂ (obtained according tothe process of example 1) in 20 ml of dichloromethane were introducedinto a reactor under a nitrogen atmosphere. 8 g of Me₃SiBr were addedand the reaction mixture was stirred at ambient temperature for hours.After evaporation under vacuum, 6.6 g of a yellow oil were obtained.Proton NMR and elemental analysis confirm the formation of(Me₃SiO)₂P(O)—(CH₂)₃—S₄—(CH₂)₃—P(O) (OSiMe₃)₂

EXAMPLE 3 Preparation of (HO)₂P(O)—(CH₂)₃—S₄—(CH₂)₃—P(O)(OH)₂

5 g of the compound (Me₃SiO)₂P(O)— (CH₂)₃—S₄—(CH₂)₃—P(O)(OSiMe₃)₂obtained according to the process of example 2 were introduced into areactor and 30 ml of methanol were added. After stirring at 40° C. for 6hours and evaporation under vacuum, 2.9 g of a yellow solid wereobtained. Proton NMR and elemental analysis confirm the formation of(HO)₂P(O)—(CH₂)₃—S₄—(CH₂)₃—P(O)(OH)₂.

1. A compound corresponding to the formula:(RO)_(2-t)R¹_(t)P(O)—O_(x)—(CH₂)_(y)—S_(z)—(CH₂)_(y)—OX—P(O)(OR)_(2-t)R¹ ₂  (I) inwhich: R represents a hydrogen, an alkyl, an aryl, a trialkylsilyl, atrialkylamino or an alkali metal; R¹ represents an alkyl or an aryl; xis 0 or 1; y is an integer from 1 to 22; z>3 t is 0 or
 1. 2. Thecompound as claimed in claim 1, wherein R is an alkyl radical havingfrom 1 to 6 carbon atoms.
 3. The compound as claimed in claim 1, whereinR is trialkylsilyl group R′₃Si— in which the R′ substituents representidentical or different alkyl groups having from 1 to 3 carbon atoms. 4.The compound as claimed in claim 1, wherein R is a trialkylamino groupR″₃N— in which the R″ substituents represent identical or differentalkyl groups having from 1 to 5 carbon atoms.
 5. The compound as claimedin claim 1, wherein R is an alkali metal chosen from Na and K.
 6. Thecompound as claimed in claim 1, wherein x=0.
 7. The compound as claimedin claim 6, it corresponding to the formula(RO)₂P(O)—(CH₂)_(y)—S_(z)—(CH₂)_(y)—P(O)(OR)₂  (II).
 8. The compound asclaimed in claim 6, corresponding to the formula(RO)R¹P(O)—(CH₂)_(y)—S_(z)—(CH₂)_(y)—P(O)(OR)R′  (IV).
 9. The compoundas claimed in claim 1, wherein x=1.
 10. The compound as claimed in claim9, corresponding to the formula(RO)₂P(O)—O—(CH₂)_(y)—S_(z)—(CH₂)_(y)—O—P(O)(OR)₂  (III).
 11. Thecompound as claimed in claim 9, corresponding to the formula(RO)R¹P(O)—O—(CH₂)_(y)—S_(z)—(CH₂)_(y)—O—P(O)(OR)R¹  (V).
 12. Thecompound as claimed in claim 1, wherein z is on average equal to
 4. 13.The compound as claimed in claim 1, characterized in that wherein R¹ isan alkyl radical having from 1 to 18 carbon atoms or an aryl radicalchosen from the phenyl, benzyl or tolyl radicals.
 14. The compound asclaimed in claim 1, wherein y is an integer from 2 to
 4. 15. A compositematerial comprising an elastomeric matrix and an inorganic filler,wherein the material comprises a compound as claimed in claim 1 as acoupling agent.
 16. The material as claimed in claim 15, wherein theinorganic filler is an oxide, a hydroxide, a carbonate or asilicoaluminate.
 17. The material as claimed in claim 15, wherein theinorganic filler is a metallic material chosen from steels, aluminum andcopper.
 18. A process for the preparation of a compound as claimed inclaim 7 in which each of the R groups is an alkyl Ra and z=4, wherein:during a first stage, the trialkoxyphosphonate P(ORa)₃ (VI) is reactedwith the dibromoalkane Br—(CH₂)_(y)—Br (VII) at a temperature of theorder of 140° C. in order to obtain Br—(CH₂)_(y)—P(O)(ORa)₂ (VIII),during a second stage, the phosphonate Br—(CH₂)_(y)—P(O)(ORa)₂ (VIII) isreacted with Na₂S₄ under reflux of the methanol in order to obtain thecompound (RaO)₂P(O)—(CH₂)_(y)—S₄—(CH₂)_(y)—P(O)(ORa)₂(IIa).
 19. Aprocess for the preparation of a compound as claimed in claim 7 in whicheach of the R groups is a trialkylsilyl R′₃Si—, comprising reacting thecompound (RaO)₂P(O)—(CH₂)_(y)—S₄—(CH₂)_(y)—P(O)(ORa)₂ (IIa) with atrialkylsilyl bromide R′₃SiBr in a ¼ molar ratio in order to obtain thecompound (IIb) (R′₃SiO)₂P(O)—(CH₂)_(y)—S₄—(CH₂)_(y)—P(O)(OSiR′₃)₂.
 20. Aprocess for the preparation of a compound as claimed in claim 7 in whichR is H, comprising hydrolyzing a compound(Ra)₂P(O)—(CH₂)_(y)—S₄—(CH₂)_(y)—P(O)(ORa)₂ in which Ra is an alkyl orhydrolyzing or alcoholyzing a compound(R₁₃SiO)₂P(O)—(CH₂)_(y)—S₄—(CH₂)_(y)—P(O)(OSiR′₃)₂.
 21. A process forthe preparation of a compound as claimed in claim 10 in which Rrepresents H, wherein: during a first stage, P(O)Cl₃ is reacted withHO(CH₂)_(y)Cl in stoichiometric proportions in order to obtain thecompound Cl(CH₂)_(y)OP(O)Cl₂; during a second stage, the compoundCl(CH₂)_(y)OP(O)Cl₂ is hydrolyzed in order to obtain the compoundCl(CH₂)_(y)OPO₃H₂; during a third stage, Cl(CH₂)_(y)OPO₃H₂ is reactedwith Na₂S₄ under reflux of the methanol and then an ion exchange iscarried out in order to obtain the compound(HO)₂P(O)—O—(CH₂)_(y)—S_(z)—(CH_(z))_(y)—O—P(O)(OH)₂.